Recently, the demand of portable electronic products such as laptop computers, video cameras, and mobile phones is dramatically increasing and development of electric vehicles, hybrid electric vehicle, energy storage batteries, robots, and satellites is briskly proceeding, and in keeping with this trend, studies are actively being conducted on high performance secondary batteries that can be recharged and used repeatedly.
Currently, available secondary batteries include nickel-cadmium batteries, nickel-hydrogen batteries, nickel-zinc batteries, lithium secondary batteries, and the like, and among them, lithium secondary batteries are gaining attention in many fields due to advantages of charging and discharging freely in the absence of a memory effect, a very low self-discharge rate, and a high energy density when compared to nickel-based secondary batteries.
Such a secondary battery may be used as a single battery cell, but for use in a high voltage and/or high capacity power storage device, may be used by connecting multiple battery cells in series and/or in parallel. Also, a secondary battery may be used in the form of a battery pack including a plurality of battery cells and various battery management apparatuses to control the overall charging and discharging operations of the battery cells.
In the research and development of the battery pack, safety improvement of the battery pack or the battery cells is sought to achieve. In the event of an electrolyte decomposition reaction and a thermal runaway phenomenon caused by heat generated due to an internal short circuit, overcharge, overdischarge, or other reasons, the battery cell may explode due to a rapid increase in internal pressure. Particularly, the battery management apparatus provided in the battery pack measures and monitors the voltage for each battery cell to prevent an explosion accident caused by overcharge. If the voltage of the battery cell exceeds a threshold voltage, that is, if the battery cell is overcharged, the battery management apparatus turns off a charge/discharge switch installed on a charge/discharge line of the battery pack to interrupt a high current path. Also, if this protection measure fails, a fuse installed on the charge/discharge line of the battery pack works to protect the battery cell from damage that may subsequently occur due to overcharge. That is, when the battery management apparatus determines that there is a risk of explosion in the battery cell due to overcharge, the battery management apparatus melts the fuse installed on the charge/discharge line of the battery pack to break a circuit to prevent the battery cell from being charged any longer.
The management apparatus transmits and receives data to and from an external device via a communication line to execute various control algorithms. Thus, the management system is generally manufactured in the form of an integrated circuit (IC). However, with the recent development of wireless Internet and use of a high output battery pack, noise or electromagnetic waves of various frequencies may affect the IC. As a result, an error may occur while the IC is measuring the voltage of the battery cell.
If the battery management apparatus determines that the battery cell is overcharged based on an incorrectly measured voltage value and melts the fuse installed on the charge/discharge line, the battery pack becomes unusable. In this case, to render the battery pack usable, a manufacturer or an operator should pick up the battery pack, check the state of the battery cell, and then replace the fuse.
As described in the foregoing, when the fuse included in the battery pack is melted to break a circuit based on an incorrectly measured voltage base, an economic loss and a time loss is considerable. Accordingly, there is a rising need for an algorithm that may reduce the likelihood that a malfunction will occur during a battery cell voltage measuring operation and even a fuse melting operation.